1. Field of the Invention
The present invention relates to monitoring systems and devices and in particular to monitoring systems for use in the monitoring of workers operating in dangerous environments or under potentially dangerous conditions. The invention is especially applicable to the monitoring of personnel operating in confined spaces as are frequently encountered in the chemical, petrochemical and refining industries.
2. Description of the Related Art
In the following, reference will be made to the petrochemical industry and petrochemical plants. This is not intended to be limiting on the present application and in the present context is intended to include also chemical plants and refineries and all other locations where workers are required to work within confined spaces or under dangerous conditions where safety monitoring is required such as within boilers, tanks, tubing systems, ships holds or the like. Where reference is made to confined spaces, this term is generally understood in this context to refer to spaces which are not normally accessible and which are not usually intended as workplaces.
Petrochemical plants are generally designed to run around the clock with little or no day-to-day maintenance. At the end of a production run or as part of the long-term maintenance programme, the plant will be shut down and what is known in the industry as a “shutdown” or “turnaround” will take place. Such a turnaround will usually entail a thorough cleaning and complete overhaul of the plant. It is also an opportunity to upgrade the plant or redesign some aspects to improve efficiency or to adapt it for a different product or different working conditions. For some plants a turnaround may take place every 3 months; for other plants this may only take place once every three years or more. In all cases, the turnaround procedure is critical since the expense involved in keeping the plant inactive can amount to several millions of dollars per day.
For this reason, turnarounds are minutely planned well in advance, usually to coincide with a slack period in the yearly production cycle. These periods are usually spring and autumn, since summer is unsuitably hot for anything other than emergency work and for refineries, winter is usually the peak production season. During a turnaround, a huge contingent of personnel will descend on the plant. While many plants may function with less than 50 staff, a turnaround may involve up to 5000 people over e.g. a six-week period. These persons must be accommodated, entertained, supervised and supplied and the turnaround may operate 24 hours a day until the plant is recommissioned. In order to cope with the logistics of such events, specialised turnaround contractors are used, employing large numbers of temporary workers of varying skill levels.
Because of the nature of the environment, the work is potentially very dangerous. This factor, combined with the limited mental ability of certain workers and the time pressure under which the operation takes place result in the need for exceptional attention to all aspects of safety. To achieve this level of safety requires a yet further quantity of safety monitoring personnel. For work within a confined space, as is the case for personnel cleaning within a refinery column, a safety officer must be on duty for each person present within the column. The safety officer is required to remain immediately outside the access opening and continually monitor the work taking place within the column. In the event that any sort of emergency occurs, the safety officer is immediately available to intervene and commence the appropriate rescue procedure for the worker or workers within the column. Most of the time however, the safety officers only intermittently observe. Such inactivity leads to boredom and frequently they may become distracted, lose concentration and even fall asleep or go off for a coffee. A major problem with work in such environments is the lack of continuous attention to safety and a tendency by both workers and “safety” officers to cut-corners wherever possible or shirk responsibility. Even when the safety officers act conscientiously, since much of the work takes place out of sight within the confined space, rigorous observation of the work is difficult or incomplete.
Under certain circumstances, workers may be required to work within a sealed environment. This may be the case where the levels of noxious gas are so high that the area must be sealed completely. Such situations may occur when breaking up benzine columns where a hermetically sealed tent is erected over the complete structure. It can also occur that the contents of the plant e.g. a catalytic column are unstable in air. In such circumstances, it may be necessary to operate in an environment of nitrogen. In both of these examples the workers are required to operate with breathing equipment. Clearly, it is impossible for the safety officer to effectively monitor without entering the sealed environment and being exposed to the danger himself.
In assuring the safety of operating personnel, the safety officer may also be required to monitor the identity and/or qualification of the personnel. This may frequently be achieved simply by knowledge of the individuals and the nature of the different operations that they are authorised to conduct. Under situations where many individuals, in particular temporary and contract staff, are employed, such checks may be conducted by the use of authorisation certificates and identity cards. In this way, only an authorised and competent person may be permitted to conduct a particular operation, e.g. welding using oxy-acetylene within a given environment such as a fractionating column.
An additional function of the safety officers may be the periodic measurement of the air composition at the workplace. This may involve the introduction of a hand held gas analyser through the access man-hole into the column interior and reading out the result. If the gas analyser gives a reading indicating that noxious or flammable gases are present, the safety officer is required to immediately alert and evacuate any personnel present within the column. Periodic measurement of the air composition at the access opening does not always provide a reliable indication of the actual condition under which the personnel are working. In addition to possible risks of explosion, many of the gases encountered are potentially dangerous, especially in large doses. At present it has been customary to carry out urine tests on workers at the end of every shift in order to determine levels of exposure to particular chemicals. If excess levels are encountered in the urine, the worker may be barred from working during the following shift.
In addition to safety monitoring of the workplace, it is essential that periodic inspection of the work takes place to assure that it is correctly and safely executed. Inspection may be carried out by the safety officers or other members of the contracting team. Additionally or instead, it may be carried out by personnel from the refinery or plant in order to guarantee the quality of the work. Such inspections are however difficult to achieve when the work proceeds at a high rate. Frequently, sections of the plant will have been reassembled prior to an inspection taking place. In the case of refinery fractionating columns, such columns are built up from large numbers of layers of dishes. Once a layer has been completed it is no longer possible to determine whether the layer below has been correctly assembled.
There is thus a need for a system whereby adequate monitoring of a workplace, in particular a confined space, can be achieved while fulfilling all reasonable requirements of safety and also allowing for inspection of the work at all stages of its completion. At present, no system is available which meets these stringent requirements.
In the field of security systems, in particular building and site security systems, it is well known to provide video monitoring equipment whereby a security officer at a central location can monitor various remote locations around the building. Such systems may employ a number of video cameras which feed back images to the central location where they can be viewed on an appropriate video screen or on a number of video screens. A device employing video cameras for building security is known from U.S. Pat. No. 5,382,943. Such devices are intended to provide a level of visual security sufficient for e.g. prevention against robbery or detection of intruders. They may also be provided with a gas sensor for the purpose of fire detection. Such systems are however designed to be permanently integrated into a building environment and are not adapted for mobile deployment at a workplace. In particular, the use of radio transmission between the video camera and monitor is unsuitable for use in the context of refinery fractionating columns where transmission is impeded by the steel wall of the column. Furthermore, they are generally of a construction and configuration which makes them unsuitable for use in a workplace.
Various alternative systems have also been suggested utilising two way video and audio links, allowing an individual at a central location to communicate with an individual at a remote location and vice-versa. Such devices may be used in providing guidance for the performance of complicated procedures such as the servicing of machines. A system for instructing personnel in the operation of machinery at a plant is known from U.S. Pat. No. 5,844,601. This system is neither contemplated nor adapted for ensuring the safety of the operating personnel.